The present invention relates to a gear pump. Conventional hydraulic gear pumps consist typically in a casing, of which the interior is fashioned with two intercommunicating cylindrical chambers, and accommodated internally of the chambers, two toothed wheels or gears engaged in constant mesh. One such gear is integral with or keyed to a drive shaft supported in the pump casing and projecting at one end to allow of being coupled to a power source, whilst the remaining gear is integral with or keyed to a driven shaft, likewise supported in the casing.
One of the cylindrical chambers is connected to an inlet pipeline through which oil will be drawn from a tank, and the remaining chamber is connected to a pressure pipeline.
Oil from the tank is trapped by the meshing teeth of the gears and forced into the pressure pipeline, according to a principle already familiar to those skilled in the art.
The casing of the pump is composed of a central body, and two end covers between which the central body is sandwiched and bolted.
Pressure-loaded bearing blocks may also be located between the two covers and the body of the pump, affording bores to accommodate the two shafts. One particularly noticeable problem experienced with this type of pump is the noise generated by the meshing action of the gears in trapping the oil and transferring the flow from the inlet pipeline to the pressure pipeline.
To ensure that the pump will deliver an acceptable level of efficiency in combination with a low level of noise, each tooth of the driving gear must make contact on both flanks with the teeth of the driven gear.
This is a question that tends, within the scope of the prior art, to be addressed by the adoption of purely geometrical solutions, aimed at optimizing tooth profiles and manufacturing tolerances; the problem can indeed be overcome in this way, albeit incurring considerable extra production costs.
In many instances, manufacturing tolerances will be such as to disallow any effective and repeatable solution to the problem.
The prior art also embraces the notion of splitting each gear into two parts exhibiting sets of teeth staggered one from the other.
Such a technique likewise overcomes the problem in question, though the costs of realization are high. The object of the present invention is to overcome the aforementioned noise problem by modifying the resultant of the forces acting on the driven shaft and the drive shaft (namely, the pressure forces on the gears, and the forces generated by gear tooth contact), through the application of a force either to the bearing block or directly to the shaft.